The maturation of mammalian oocytes in vitro has been found by several investigators to be a developmentally deficient process relative to subsequent fertilizability and embryonic potential. Recently, however, studies in this laboratory and others have demonstrated that under certain conditions of culture, mammalian oocytes are capable of apparently normal maturation in vitro. The proposed project is designed to systematically study the fertilizability and embryonic potential of mammalian oocytes matured in vitro under the highly defined conditions developed in this laboratory. the procedures to be employed include a defined bioassay for in vitro maturation, surgical ovum transfers, and analytical methods (cellular and molecular) for the determination of normalcy among maturing oocytes and developing embryos. Analyses to be carried out include cytogenetics ultrastructure and patterns of polypeptide synthesis. This study will lead to a clearer understanding of the required cellular and molecular processes which occur during oocyte maturation in vivo, which result in mature oocytes capable of fertilization and further embryogenesis. It is anticipated that specific deficiencies characterizing oocytes matured in vitro will be identified for future application to highly specific contraceptive methodology.